Safety valve assembly

ABSTRACT

Opening and closing of a subsurface safety valve is regulated by the pressure communicated to the valve through a tubing string which extends to the well&#39;&#39;s surface. The valve is retrievable through the tubing string and well production is through a casing string which surrounds the tubing. Control fluid in the tubing string is maintained at or above a predetermined pressure and a drop to a lower pressure due to wellhead damage or the like causes the valve to automatically close. The control fluid may be injection gas used to artifically produce the well. In the latter modification, the valve remains open so long as a predetermined injection gas pressure is maintained.

United States Patent 191 Garrett [451 Aug. 28, 1973 SAFETY VALVEASSEMBLY [75] Inventor: Henry U. Garrett, Houston, Tex.

[73] Assignee: Brown 011 Tools, Inc., Houston, Tex.

[22] Filed: Oct. 14, 1971 [21] App]. No.: 189,079

Related U.S. Application Data [63] Continuation-impart of Ser. No.173,360, Aug. 20,

3,294,174 12/1966 Vincent 166/224 Primary Examiner-James A. LeppinkAttomeyCarlos A. Torres et al.

[ ABSTRACT Opening and closing of a subsurface safety valve is regulatedby the pressure communicated to the valve through a tubing string whichextends to the wells surface. The valve is retrievable through thetubing string and well production is through a casing string whichsurrounds the tubing. Control fluid in the tubing string is maintainedat or above a predetermined pressure and a drop to a lower pressure dueto wellhead damage or the like causes the valve to automatically close.The control fluid may be injection gas used to artifically produce thewell. In the latter modification, the valve remains open so long as apredetermined injection gas pressure is maintained.

9 Claims, 6 Drawing Figures PATENTED A6928 I975 SHEU 1 0f 2 A TTOE/VEYSPAIENTEDMI928 ms 3354.597

sum 2 BF 2 A- Tm an-Q41, BY fiaaa ATTORNEYS SAFETY VALVE ASSEMBLY Thepresent invention is a continuation-in-part of U. S. Pat. applicationSer. No. 173,360, filed Aug. 20, I971, entitled AUTOMATIC CHOKE.

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates generally to valving means for controlling the flow offluids through fluid conductors. In an exemplary, specific descriptionof the preferred form of the present invention, the field of theinvention relates to retrievable, surface operated safety valvesdesigned to be employed at a subsurface location within an oil or gaswell where well production is through the well casing. The primarypurpose of the valve is to automatically terminate the flow of highpressure petroleum fluids from the well in the event of damage to orinoperability of the restraining structure at the well head.

As used herein, the term fluids is intended to include both liquids andgases and the term casing is intended to include any fluid conduitthrough which a smaller fluid conduit extends axially.

2. Brief Description of the Prior Art The majority of prior art deviceswhich are intended to automatically terminate the flow of high pressurepetroleum fluids from a well in the event of well structure damage orinoperability are subsurface valves which close in response to either adrop in the pressure of the petroleum fluids or to an increase in therate of flow of the fluid through the well. The subsurface position ofthe valve protects it from surface damage and the valve functions as asafety device which prevents a well blowout in which petroleum fluidsflow uncontrollably from the well.

Many of the prior art safety valves of the type being considered hereinare retrievable in that they are designed to be positioned in andretrieved from the production tubing while the tubing is in place. Theseretrievable valves normally include a control mechanism which, dependingon the type involved, senses a drop in production fluid pressure or anincrease in flow rate and employs the potential energy of a compressedspring or a gas charged chamber to effect movement of valve closureelements which terminates flow through the production string. Normally,also, the production string is a string of tubing which is surrounded bya larger casing string. Conventional packing means are usuallypositioned between the tubing and easing strings at a subsurfacelocation so that all well fluids are forced to flow through the centralproduction string. Most of the prior art safety valves are designed tobe employed in the typical well configuration where production isthrough the central tubing string.

Since the conventional, self-contained safety valves close only on theoccurrence of either a low pressure or an increased flow rate, it isoften impractical to test the valve when it is in its subsurfacelocation. In the typical well, production fluid is normally being fedinto a restraining pipe line or storage tank under controlled pressureand flow conditions and the only time when the well fluids drop belowthe closure pressure or move at a rate greater than the closure rate ofthe safety valve is when control of the well has been lost. In anyevent, even if the desired low pressure or high flow rate conditions forthe production fluid could be provided at the well surface for purposesof testing the downhole valve, the equipment required to complete thetest and the danger associated with the test would likely render testingof the downhole valve impractical.

In some cases, it is desired to close the subsurface safety valve andalso to close the well with valves at the wellhead. Simultaneous closureof both the wellhead valve and the subsurface valve is desired forexample, where off-shore platforms are being readied for a threatenedhurricane which might damge or destroy the confining wellhead structure.Where self-contained pressure or flow rate responsive valves areemployed, such valves cannot normally be closed with the wellhead valvesclosed since the pressure and flow rate values under these conditionsare not adequate to cause closing of the subsurface valve. Because ofthe amount of time required and the expense involved, it is impracticalto retrieve the self-contained valve in each well and replace it with aplug or other suitable device each time a hurricane threatens. If thesubsurface valve is not closed before the hurricane strikes, there is adanger that malfunction will prevent the subsurface valve fromautomatically closing and that damage to the wellhead structure willresult in a blowout.

Another prior art safety valve which overcomes several of theshortcomings associated with self-contained flow responsive or pressureresponsive safety valves employs a small control line which extends froma subsurface valve to the well surface. The control line is filled witha pressurized fluid which keeps the valve open. Loss of pressure in theline releases the closure elements of the subsurface valve which permitsthe valve to close and terminate all flow through the tubing string.

In systems of the foregoing type, the control line is normally arelatively small conduit which must be accommodated between the tubingstring and the surrounding well casing. The need for a third conduit inaddition to the casing and tubing string is undesirable in manyapplications and the small control line is subject to breakage orcrimping which would prevent proper operation of the safety valve.Moreover, the small control line and the tubing string must be insertedinto the well simultaneously and special equipment is needed for thispurpose.

In the self-contained safety valves described previsouly, pressureresponsive valves cannot normally be employed where the well must beartifically produced by gas lift techniques because of the low pressurepresent in the production fluid column of the gas lifted well. Moreover,neither of the prior art safety valves described previously is adaptedfor applications where the well fluid is to flow to the wellhead throughthe casing rather than the tubing string.

SUMMARY OF THE INVENTION The present invention provides a surfacecontrolled, subsurface safety valve designed to be employed in an oil orgas well in which the petroleum fluids are carried to the wellheadthrough the well casting. The valve is retrievable and may be run in aconventional tubing string which extends through the casing andfunctions as a control string. Operation of the valve is regulated bythe pressure of the control fluid contained within the tubing stringwhich in turn may be surface regulated.

In the preferred form of the present invention, a drop in the controlfluid pressure causes the valve to close.

Surface control is thus effected without the need for a separate controlline extending between the tubing and easing. Since the valve is surfacecontrolled, it may be tested and it may also be closed even when thewell is closed at the wellhead. The valve may be retrieved withouthaving to remove the tubing string from the well. This feature of thepresent invention permits the valve to be easily recovered forreplacement or repair or for changing operating pressure values.

The assembly of the present invention may also be used in a gasinjection system where pressurized gas is injected int the casingthrough the control string. When used in an injection system, the valveis held in open position so long as the injection gas pressure remainsabove a predetermined value.

A landing nipple receives the valve and holds it at its subsurfacelocation. The nipple is equipped with a blast collar which preventsabrasive well fluids from abrading and eventually cutting through thecasing string wall. The valve may be positioned within or recovered fromthe landing nipple by pumping it through the tubing string or with theuse of conventional wireline tools and techniques. Anchoring and sealmeans are provided along the external surface of the valving means toprovide sealing engagement and releasable anchoring with the landingnipple.

The foregoing as well as other features and advantages of the presentinvention will be more readily appreciated from the followingspecification, claims and related drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectionschematically illustrating the valve of the present invention in openposition;

FIG. 2 is a view similar to FIG. 1 illustrating the valve in closedposition;

FIG. 3 is a vertical elevation, partially in section illustratingdetails in the construction of the valve assembly of the presentinvention;

FIG. 4 is a view similar to FIG. 3 illustrating the valve in openposition;

FIG. 5 is a vertical section schematically illustrating a modified formof the present invention designed for use in gas lift assemblies; and

FIG. 6 is a view similar to FIG. 5 illustrating the valve in closedposition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The safety valve assembly ofthe present invention is indicated generally at 10 in FIG. 1. Theassembly 10 is illustrated in position within a well casing C whichextends between a subsurface location (not illustrated) and a surfacewellhead (not illustrated). A conventional tubing string T extendsaxially within the casing C and conventional packing means P forms afluid-tight seal between the tubing and casing. A retrievable valveindicated generally at 11 is illustrated in position within a landingnipple 12 which forms a portion of the tubing string T. The assembly 10includes valving means indicated generally at 13 which cooperate withradial ports 14 formed through the landing nipple 12 to povide aclosable flow passage between the valves upstream side U in the tubing Tand its downstream side D in the casing C. Fluid flow through the openvalve is in the upstream to the downstream direction as depicted by thearrows A.

The valving means 13 includes a stationary seat 15 and an axiallymovable stem 16. A coil spring 17 urges the valve stem 16 toward closed,seating engagement with the seat 15 against the opening force exerted bythe pressure of the petroleum fluid acting at the valve's upstream sideU.

Upper and lower packing means 18 and 19, respectively, provide afluid-tight seal between the retrievable valve 11 and the surroundinglanding nipple l2. Releasable anchoring dogs 20 are provided at theupper end of the valve 11 to provide anchoring engagement with thelanding nipple 12. The upper end of the valve 11 is equipped with afishing neck 21 by which the valve is moved into position within andsubsequently retrieved from the landing nipple 12.

Well fluids flowing in the direction of the arrow A travel from asubsurface point downstream of the packer P through the lower portion ofthe control conduit 12 and up into the flow passages of the valvingmeans 11. As the fluid exits the radial openings 14, it strikes a blastcollar 22 which deflects the flow to protect the surrounding casing wallfrom the abrasive action caused by fluid carried particles. Once thefluids are on the downstream side U within the annular area between thecontrol tubing 12 and the surrounding casing C, they are directedupwardly to the wellhead where they are carried away by a pipeline ordeposited in suitable storage containers.

In FIG. 2 of the drawings, the valve closure element 16 is illustratedseated against the valve seat 15. In the latter position, fluid flowthrough the valving assembly is completely terminated. As will befurther described hereinafter, movement of the closure member 16 isregulated as a function of the pressure of a control fluid contained atT-l within the control conduit T, above the valve 11. In the preferredform of the invention, when the pressure of the control fluid at T-ldrops below a predetermined value, the closure member 16 isautomatically moved by the spring 17 into the seated positionillustrated in FIG. 2.

Referring now to the detailed illustration of the valving assembly 10shown in FIGS. 3 and 4 of the drawings, FIG. 3 illustrates the valvingmeans 11 in closed position. The landing nipple 12 is threadedly engagedat its upper and lower ends to tubular conduits which form a portion ofthe control tubing string T. Above and below the landing nipple 12, thetubing string T is formed of conventional, tubular pipe with the upperpipe section extending to the wellhead and the lower section extendingbelow the packer P. Well fluids are admitted into the internal portionsof the well conduit T below the packing P by any conventional means (notillustrated).

The landing nipple 12 is restricted at its lower end 23 to provide alower limit of travel for the valve 11. The valve 1 1 includes acentrally ported shoe 24 threadedly engaged to the lower end of atubular housing section 25. The shoe 24 is externally tapered to assistin guiding the valve downwardly through the tubing string T duringinitial positioning of the valve. The lower packing 19 which is securedbetween an outwardly extending housing section shoulder and the upperend of the shoe 24 provides a slidable, fluid tight seal between thelower valve end and the nipple 12. Flow passages through the open valveare formed by radial ports 26 opening through the housing section 25 andby a central opening 27 extending axially through the lower portion ofthe housing. The valve seat is formed adjacent the upper end of theopening 27.

-A control housing section 28 is threadedly engaged to the upper end ofthe valve housing 25. An externally tapered collar 29 threadedly engagedabout the upper end of housing 28 cooperates with an outwardly developedshoulder on the housing to secure the upper packing 18 in position. Thepacking 18 is formed by chevron type packing overlying a thin metallicsupport ring 18a which in turn overlies a resilient O-ring seal 18b. Thepacking seal 18 and components 180 and 18b cooperate to provide afluid-tight seal between the outer surface of the control housing 28 andthe inner surface of the landing nipple 12. The control housing 28includes an upper bellows housing section formed in part by a bellowssupport member 30 threadedly engaged to the upper end of the housing 28.A tubular bellows valve housing 31 is threadedly engaged to the upperend of the member 20. A tubular bellows dome housing 32 is threadedlyengaged to the upper end of housing 31 and a dome cap member 33 isthreadedly engaged into the upper end of the housing 32. The member 33is centrally ported for removably carrying a conventional gas valve 34and the upper end of the ported opening is sealed by a threadedlyengaged plug 35.

The upper end of the member 33 is threadedly engaged to a spreadermember 36 which provides a connecting structure between the main body ofthe valve 1 l and the tubular fishing neck 21 and cooperates with thedogs to anchor the valve 11 in place. The upper end of fishing neck 21includes an outwardly extending shoulder 21a by which the entireassembly may be grasped by a suitable placement or retrieval tool. A dogretaining collar 37 is slidably carried over the fishing neck 21 and isemployed to support a plurality of the anchoring dogs 20. The upper endof the collar 37 is equipped with an outwardly developed shoulder 37aandthe lower end is provided with a skirt 37b. An inwardly developedshoulder 37c in the skirt 37b is adapted to engage an outwardly directedshoulder 20a formed at the upper end of each of the dogs 20 to preventaxial separation of the collar and dogs while simultaneously permittinglimited pivotal motion of the dogs. The upper end of the spreader member36 is externally tapered at 36a to provide a wedging surface whichcooperates with internally tapered surfaces at the lower end of each ofthe dogs to pivot the lower dog ends outwardly when the dogs are moveddownwardly over the tapered spreader surface. The lower dog ends includeanchoring projections 20b which are adapted to pivot outwardly into anipple recess 38 when the retaining collar 37 is moved axiallydownwardly over the fishing neck 21 As will be more fully described, theillustrated construction permits the valving assembly 11 to be lockedinto the landing nipple 12 where it is firmly maintained until beingreleased by a suitable retrieving means.

Opening and closing of the valve 11 is regulated by the pressureexisting in the tubing or control conduit T above the point of thepacking seal 18 at T-l. The pressure at T-l is communicated through aplurality of ports 39 extending through the connecting member 36, intoan annular area 40 between the valve 11 and the surrounding nipple 12,and into the bellows housing 28 through openings 41. Internally of thehousing 28, a tubular bellows section 42 of conventional constructionextends axially between the lower end of the bellows support 30 and anexternally developed shoulder on an actuator 43. The bellows 42cooperates with other seals illustrated in the drawings to maintain afluid tight seal between an external bellows area 44 and an internalbellows area 45 while permitting axial movement of the actuator 43. Theupper end of actuator 43 engages an axially movable bellows valve 46which is adapted to move between upper and lower sealing surfaces 47 and48, respectively. As will be seen, axial movement of the bellows valve46 functions to isolate the lower internal bellows area 45 from an upperinternal bellows area 49. Upper and lower O-ring seal 50 and 51,respectively, are carried by the bellows valve to provide sealingengagement with the upper and lower seats 47 and 48, respectively.

The primary valve member 16 adapted to regulate the flow of petroleumfluids through the assembly is a substantially tubular piston adapted tobe moved axially within the central bore of the valve housing 25.Annular packing 52 extends about the upper end of a main body section 53of the member or piston 16 to provide a continuous sliding seal betweenthe piston and the walls of the surrounding housing bore. The seal 52 isheld in position by a threadedly engaged upper end piece 54. The lowerend of the piston 16 includes a centrally apertured body piece 55secured to an internal shoulder of the main body section 53 by threadedengagement with a retaining collar 56.

An alignment stem 57 extends axially through the center of the collar 56and end piece 55 and is threaded at its upper end to a tubular springguide 58. A restricted pressure communicating input passage 59 is formedbetween the stem 57 and the end piece 55 and collar 56. Pressureexisting within the tubing string at the valves upstream end U iscommunicated through the passage 59 into a control pressure area 60acting behind the piston 16. A pressure relief passage extends betweenthe pressure area 60 and the downstream side D of the valve 11. Therelief passage is provided by a flow passage 61 formed through thecontrol housing 28, an axially extending flow passage 62 formed betweenthe member 28 and the outer surface of the actuator 43, radial passagemeans 63 extending through the member 28 and radial openings 64 formedin the nipple 12. Axial movement of the actuator 43 causes annularO-ring seals 65 and 66 to open and close the radial passages 63 toprovide valving of the relief passage. Because of the restricted size ofthe passage 59, a pressure drop occurs between the upstream side U andthe pressure control area 60 when the pressure relief passage is open.When the actuator is in its upper position as illustrated in FIG. 4, thepassage 63 is opened to permit communication with the passage 61 throughthe axial passage 62. A lower O-ring seal 67 cooperates with the seal 66to provide upper and lower seals for the passage 62. Pressure openings28a shown in dotted line prevent the development of. a pressure lockwhich would hamper movement of the actuator 43.

OPERATION In an exemplary application of the present invention, aconventional tubing string T equipped with the landing nipple 12 islowered into the well casing C in a well known manner. The nipple 12 islowered to the desired subsurface location which, for offshore wells, isnormally at a point below the water bottom. A conventional packer P isset below the nipple 12 to provide a fluid-tight seal between the casingand tubing. The valve ing means 11 is thereafter inserted into thetubing string T at the well surface and lowered through the string byany suitable means. During the lowering procedure, the dog retainingcollar 37 is held at its upper axial position over the fishing neck 21so that the enlarged portions 20b of the dogs 20 are free to pivotinwardly to their radially innermost position along the fishing neck 21.When the valve 11 is properly located in the nipple 12, the shoe 24engages the restriction 23 to prevent further downward movement. The dogretaining collar 37 is then lowered about the fishing neck 21 whichmoves the lower ends of the dogs 20 downwardly over the tapered surfaceof the spreader member 36. This spreading movement pivots the enlargedends 2012 radially outwardly into the nipple recess 38. Any upwardmovement of the valve caused by pressure induced forces or otherwisetends to spread the dogs outwardly which maintains the lockingengagement between the recess and the dogs. The setting mechanism may beretrieved from the well once the valve 11 has been properly positioned.

The lower internal bellows area 45 is filled with an incompressiblefluid such as a light weight oil or other suitable fluid. The oil isfilled to a level which extends into the upper chamber 49. The oildisplaces any compressible fluid such as air contained within theinternal bellows chamber 45. The upper chamber 49, above the oil level,is charged through the valve 34 with a suitable gas. Suitable seals areprovided through the valve construction to prevent leakage of the oiland gas contained within the internal bellows area 45 and the upperbellows chamber 49. As will be seen, the gas pressure in the chamber 49is one of three pressure values which determines the opening and closingoperation of the valve.

Once the valve 11 has been latched into position within the nipple 12, acontrol pressure is supplied to the tubing string T from the wellhead.The fluid providing the control pressure may be either a gas or aliquid. The control fluid in the string T enters the openings 41 andacts against the bellows 42 in the external bellows area 44. When thecontrol fluid pressure exceeds the pressure of the gas in the bellowschamber 49, the beliows 42 is foreshortened causing the actuator 43 tomove axially upwardly from the position illustrated in FIG. 3. When theactuator is in its upper postion illustrated in FIG. 4, the controlpressure area 60 is in pressure communication with the fluid at thedownstream end D of the valve. The pressure of the petroleum fluidsacting against the lower end of the closed valve stem piston 16 at theupstream side U moves the piston upwardly against the biasing force ofthe spring 17 to open the valve flow passages. So long as the reliefpassage extending between the control pressure area 60 and thedownstream pressure at D remains open, the pressure in the area 60 islower than that acting against the bottom of the piston at the valvesupstream side U and the resulting pressure differential maintains thevalve piston 16 in its upper, open position.

In the event the control fluid pressure decreases below a predeterminedvalue as would occur for example if the wellhead were ruptured ordamaged, the external bellows pressure at 44 is reduced permitting thegas charge in the upper bellows chamber 49 to expand the bellows andmove the attached actuator 43 axially downwardly. The downward movementseals the radial passage 63 as illustrated in FIG. 3 to terminatecommunication between the pressure control area 60 and the downstreamside of the valve. With the relief passage closed, the upstream pressureacting through the restricted passage 59 brings the pressure in thecontrol area 60 up to that existing at the upstream side of the piston16. When both pressures are substantially equal, pressure induced forcestending to move the piston are reduced to the point necessary to permitthe spring 17 to force the valve stem downwardly into its closedposition.

Overcompression or overexpansion of the bellows 42 is prevented byaction of the bellows valve 46. When the valve is in its lower positionillustrated in FIG. 3, the pressure existing within the upper bellowschamber 49 is isolated from the internal bellows area 45 to preventfurther expansion of the bellows. When the valve member 46 is in itsupper position as illustrated in FIG. 4, the incompressible fluid in thelower bellows area 45 is prevented from escaping the area so that thepressure existing in the outer bellows area 44 is prevented fromovercompressing the bellows. By this means, the bellows element 42 isprotected from damage caused by overexpansion or Overcompression.

Retrieval of the valve from its set position within the nipple 12 iseffected by lowering a suitable retrieving mechanism down to the nippleand latching onto the shoulder 37a provided on the dog support member37. The member 37 is pulled upwardly while the fishing neck 21a is heldstationary. This permits the dogs 20 to pivot inwardly and disengage thesurrounding nipple wall. The valve may then be retrieved to the surfacefor inspection, replacement or repair.

In testing the valve, it will be appreciated that pre susre within thetubing string T need only be lowered and the production flow from thewell monitored. If the production flow terminates, the valve isfunctioning properly and may be reopened by simply repressuring thecontrol fluid.

A modified form of the invention is illustrated in FIGS. 5 and 6 wherethe valving assembly has been equipped for use in a gas injectionsystem. The modification, in FIGS. 5 and 6 in similar to the inventionas already described with the exception that gas lift valves V areprovided along the tubing string T to permit gas lifting of the well. Inoperation, the valve 11 remains open to permit petroleum fluids to flowthrough the valve so long as the gas injection pressure within thetubing string T. is maintained above a predetermined value.

It will be appreciated that if desired, the safety valve assembly of thepresent invention may be modified so that the valve automatically closeswhen the control fluid pressure increases above a predetermined value.Thus, for example, the control pressure fluid may be a suitable gasmaintained at subatmospheric pressure. Upon an increase in pressureproduced by a rupture or damage to the control conduit, the pressurerelief passage would be automatically closed to permit closure of thevalve. The foregoing disclosure and description of the invention isillustrative and explanatory thereof, and various changes in the size,shape and materials as well as in the details of the illustratedconstruction may be made within the scope of the appended claims withoutdeparting from the spirit of the invention.

I claim:

1. A safety valve assembly comprising:

a. fluid conductor means for conducting fluids between first and secondspaced points;

b. control conduit means extending axially within said conductor meansbetween said first and second points for containing a control fluid;

c. flow passage means opening into said conductor means adjacent saidfirst point for conducting fluids into said conductor means;

d. valving means including:

i. a'downstream and an upstream side, said valving means connected withsaid control conduit means and movable between open and closed positionsfor respectively opening or closing said flow passage means as afunction of the pressure of said control fluid, said valving means beingmovable through said control conduit means between said first and secondpoints and including remotely actuated anchoring means for anchoringsaid valving assembly in operative position within said control conduitmeans;

ii. sealing means for forming a fluid-tight seal between said conduitmeans and said valving means;

iii. remotely operable release means for releasing said valving meansfrom anchored engagement with said conduit means whereby said valvingmeans may be released and moved through said conduit means from saidfirst to said second point;

e. pressure responsive control means included in said valving means andcommunicating with said control fluid for maintaining said flow passagemeans open while the pressure of said control fluid is within apredetermined range of values and for closing said flow passage when thecontrol fluid pressure is outside of said range, said control meansincluding:

i. biasing means tending to move said valving means into closed positionagainst pressure induced forces exerted against the upstream side ofsaid valving means;

ii. a control pressure area for exerting pressure induced forces tendingto move said valving means in a direction opposite to the valving meansmovement caused by said pressure induced forces exerted on the upstreamside of said valving means;

iii. pressure relief passage means extending between said controlpressure area and the downstream side of the said valving means;

iv. actuator means for opening and closing said pressure relief passagemeans as a function of said control fluid pressure; and

v. pressure input passage means extending between said control pressurearea and the upstream side of said valving means for forming a pressuredifferential across said valving means tending to maintain said valvingmeans open when said relief passage means is open and for terminatingsaid pressure differential when said relief passage means is closedwhereby said biasing means may move said valving means to closedposition.

2. A safety valve assembly as defined in claim 1 wherein:

a. said control means includes a bellows area confined within saidvalving means and separated from said control fluid by movable bellowsmeans; and

b. said actuator means is connected for movement with said bellows meansfor opening said pressure relief passage means when the pressure of saidcontrol fluid is above a predetermined value and for closing said reliefpassage means when said control fluid pressure drops below said value.

3. A safety valve assembly as defined in claim 2 wherein:

a. said bellows area includes first and second chambers separated fromeach other by bellows valve means;

b. said bellows valve means is operable between open and closedpositions by movement of said bellows means;

c. an incompressible fluid is contained within said first chamber and atleast a portion of said second chamber; and

d. said bellows valve means is closed by movement of said bellows meansbeyond a predetermined amount in a given direction to confine saidincompressible fluid within said first chamber to prevent furtherbellows means movement in the same direction.

4. A safety valve assembly as defined in claim 3 wherein:

a. said fluid conductor means includes a tubular well conduit forconducting oil or gas from a well;

b. said second point is adjacent the wellhead and said first point isadjacent a subsurface location in said well;

c. said control conduit means includes a tubular well conduit extendingaxially within said conductor means between said subsurface location andsaid wellhead; and

d. said valving means includes pressure responsive control meanscommunicating with said control fluid for maintaining said flow passagemeans open while the pressure of said control fluid is above apredetermined value and for closing said flow passage when the controlfluid pressure drops below said valve.

5. A safety valve assembly as defined in claim 4 further including:

a. packing means extending between said control conduit means and saidwell conduit for forming a fluid-tight seal therebetween;

b. fluid inlet means opening into said control conduit on the upstreamside of said packing means;

0. fluid outlet means included in said flow passage means and openingout of said control conduit on the downstream side of said packing meanswhereby fluid at the downstream side of said packing means entering saidinlet means is confined to move through said control circuit means andout of said outlet means into said fluid conductor means;

and

d. said valving means includes cooperating valve closure means forterminating flow between said inlet and outlet means.

6. A safety valve assembly as defined in claim 5 wherein:

a. said biasing means includes a coil spring; b. said valve closuremeans includes piston means movable axially within a tubular valvehousing;

wear of said fluid conductor means is prevented.

8. A safety valve assembly as defined in claim 7, wherein said controlconduit means includes gas lift valve means between said spaced pointsfor injecting control fluids from said control conduit means into saidfluid conduit means.

9. A safety valve assembly as defined in claim 1 wherein said controlconduit means includes gas lift valve means between said spaced pointsfor injecting control fluids from said control conduit means into saidfluid conduit means.

1. A safety valve assembly comprising: a. fluid conductor means forconducting fluids between first and second spaced points; b. controlconduit means extending axially within said conductor means between saidfirst and second points for containing a control fluid; c. flow passagemeans opening into said conductor means adjacent said first point forconducting fluids into said conductor means; d. valving means including:i. a downstream and an upstream side, said valving means connected withsaid control conduit means and movable between open and closed positionsfor respectively opening or closing said flow passage means as afunction of the pressure of said control fluid, said valving means beingmovable through said control conduit means between said first and secondpoints and including remotely actuated anchoring means for anchoringsaid valving assembly in operative position within said control conduitmeans; ii. sealing means for forming a fluid-tight seal between saidconduit means and said valving means; iii. remotely operable releasemeans for releasing said valving means from anchored engagement withsaid conduit means whereby said valving means may be released and movedthrough said conduit means from said first to said second point; e.pressure responsive control means included in said valving means andcommunicating with said control fluid for maintaining said flow passagemeans open while the pressure of said control fluid is within apredetermined range of values and for closing said flow passage when thecontrol fluid pressure is outside of said range, said control meansincluding: i. biasing means tending to move said valving means intoclosed position against pressure induced forces exerted against theupstream side of said valving means; ii. a control pressure area forexerting pressure induced forces tending to move said valving means in adirection opposite to the valving means movement caused by said pressureinduced forces exerted on the upstream side of said valving means; iii.pressure relief passage means extending between said control pressurearea and the downstream side of the said valving means; iv. actuatormeans for opening and closing said pressure relief passage means as afunction of said control fluid pressure; and v. pressure input passagemeans extending between said control pressure area and the upstream sideof said valving means for forming a pressure differential across saidvalving means tending to maintain said valving means open when saidrelief passage means is open and for terminating said pressuredifferential when said relief passage means is closed whereby saidbiasing means may move said valving means to closed position.
 2. Asafety valve assembly as defined in claim 1 wherein: a. said controlmeans includes a bellows area confined within said valving means andseparated from said control fluid by movable bellows means; and b. saidactuator means is connected for movement with said bellows means foropening said pressure relief passage means when the pressure of saidcontrol fluid is above a predetermined value and for closing said reliefpassage means when said control fluid pressure drops below said value.3. A safety valve assembly as defined in claim 2 wherein: a. saidbellows area includes first and second chambers separated from eachother by bellows valve means; b. said bellows valve means is operablebetween open and closed positions by movement of said bellows means; c.an incompressible fluid is contained within said first chamber and atleast a portion of said second chamber; and d. said bellows valve meansis closed by movement of said bellows means beyond a predeterminedamount in a given direction to confine said incompressible fluid withinsaid first chamber to prevent further bellows means movement in the samedirection.
 4. A safety valve assembly as defined in claim 3 wherein: a.said fluid conductor means includes a tubular well conduit forconducting oil or gas from a well; b. said second point is adjacent thewellhead and said first point is adjacent a subsurface location in saidwell; c. said control conduit means includes a tubular well conduitextending axially within said conductor means between said subsurfacelocation and said wellhead; and d. said valving means includes pressureresponsive control means communicating with said control fluid formaintaining said flow passage means open while the pressure of saidcontrol fluid is above a predetermined value and for closing said flowpassage when the control fluid pressure drops below said valve.
 5. Asafety valve assembly as defined in claim 4 further including: a.packing means extending between said control conduit means and said wellconduit for forming a fluid-tight seal therebetween; b. fluid inletmeans opening into said control conduit on the upstream side of saidpacking means; c. fluid outlet means included in said flow passage meansand opening out of said control conduit on the downstream side of saidpacking means whereby fluid at the downstream side of said packing meansentering said inlet means is confined to move through said controlcircuit means and out of said outlet means into said fluid conductormeans; and d. said valving means includes cooperating valve closuremeans for terminating flow between said inlet and outlet means.
 6. Asafety valve assembly as defined in claim 5 wherein: a. said biasingmeans includes a coil spring; b. said valve closure means includespiston means movable axially within a tubular valve housing; c. saidoutlet means includes radial openings through said valve housing andsaid control conduit means; and d. said sealing means includes axiallyspaced packing carried externally of said tubular housing and disposedabove and below said radial openings for providing a fluid-tight sealbetween said housing and said control conduit means.
 7. A safety valveassembly as defined in claim 6 further including shielding meansdisposed between said outlet means and said fluid conductor means forpreventing fluid flowing from said outlet means from striking said fluidconductor means whereby abrasion or wear of said fluid conductor meansis prevented.
 8. A safety valve assembly as defined in claim 7, whereinsaid control conduit means includes gas lift valve means between saidspaced points for injecting control fluids from said control conduitmeans into said fluid conduit means.
 9. A safety valve assembly asdefined in claim 1 wherein said control conduit means includes gas liftvalve means between said spaced points for injecting control fluids fromsaid control conduit means into said fluid conduit means.